Dual-fuel engines are known in which the main fuel is typically natural gas with diesel oil used as the secondary fuel, especially as pilot fuel to control burning and to initiate and stabilize ignition. In the design of liquid fuel injection systems, there are many technical problems embracing such matters as providing suitable pumps, spray nozzles, and combustion chambers for the delivery, atomization and burning of the fuel in hot compressed air. Suitable fuels must be carefully chosen with due regard for such factors as viscosity, flash point, pour point, ash, sulphur content, basic sediment, water, Conradsen carbon number, cetane number, and diesel index. In designing dual-fuel engines additional problems arise, and this is particularly true when a dual-fuel engine is to be provided by adapting and converting an existing standard diesel engine.
An object of the present invention is to provide a dual-fuel engine in which at least some of the design problems and technical difficulties associated therewith are alleviated.